cmd/tracking-issue: Skip tracking issues with no labels
Created by: tsenart
This commit makes it so the tracking issue tool:
- Skips tracking issues that only have the tracking label.
- Stops paginating when no nodes are returned and the GitHub API lies about having more results.
The tracking issue tool was failing because it couldn't handle listing issues without specific label filter (the data set was too big): https://github.com/sourcegraph/sourcegraph/issues/11532